Hormones and Fertility

Defining Hormones

The term “Hormones” refers to chemicals that are secreted by glands in one part of the body; travel to another part of the body through the bloodstream; and then signal to the organ(s) there to start doing something. In reproduction, there are a number of hormones that regulate cycles of egg production, ovulation, and menstruation. If these chemicals drift out of balance, your fertility will be affected, and it can be much more difficult to become pregnant. If this happens, you may ultimately need to talk to a doctor about the following examples of fertility-related hormones.

  • Gonadotropin-releasing Hormone (GnRH) is produced in the hypothalamus. It then travels to the pituitary gland and stimulates the secretion of two other hormones, LH and FSH. GnRH is produced in pulses, and the frequency of these pulses determines whether LH or FSH is released. The pulses of GnRH speed up or slow down at different times during the reproductive cycle.
  • Luteinizing Hormone (LH) helps regulate a woman’s menstrual cycle, and an increase in LH levels triggers ovulation after a follicle has fully matured. Measuring LH levels is a common way to track ovulation. A surge in LH levels typically lasts 24-48 hours, and indicates that the mature egg has been released and is ready for fertilization.
  • Follicle-Stimulating Hormone (FSH), as the name suggests, is responsible for the development of follicles in the ovaries, the areas where individual egg cells mature before ovulation. Typical levels for a woman of reproductive age are between 4.7 and 21.5 mIU (milli-International Units)/ml.
  • Progesterone prepares the uterine lining for implantation if the egg is fertilized. There is data to suggest that progesterone may also help guide sperm to the egg. Midway through the menstrual cycle, progesterone levels increase to between 5 and 20 ng/ml.
  • Estrogen is the primary female sex hormone, produced mainly in the ovaries. Along with progesterone, estrogen promotes growth of the uterine lining and regulates the menstrual cycle. Estrogen levels also help determine the frequency of the pulses of GnRH produced by the hypothalamus. Typical levels of estrogen are between 40 and 50 picograms per milliliter.

Effects on Fertility

Working together, these hormones determine the course of the entire reproductive cycle:

  • Low-frequency pulses of GnRH tell the pituitary gland to produce FSH, which causes the follicle to develop.
  • As the follicle reaches maturity, estrogen levels eventually reach a tipping point, causing the hypothalamus to increase the frequency of GnRH pulses.
  • This signals the pituitary gland to start producing LH instead, triggering ovulation.
  • Meanwhile, the follicle - now emptied of its egg - develops into the corpus luteum, which produces progesterone, signaling the uterine lining to prepare for the egg after fertilization.


If levels of any of these hormones are too low or too high, the cycles of menstruation and ovulation can be thrown off, causing fertility problems. Hormone imbalances can be caused by a number of diseases or disorders, including Polycystic Ovary Syndrome, diabetes, drugs including antidepressants, and even stress.

Your doctor may recommend blood tests if they suspect a hormone imbalance is affecting your fertility. Hormone imbalance can be treated with drugs or injected hormones, or your doctor could try to treat the underlying issue that is causing the imbalance. Talk to your doctor about options, including lifestyle changes such as diet and exercise.